plateau....

hey everyone! So I gained about 20lbs overweight before I got pregnant in 2016. I gained an additional 30 lbs during pregnancy, had my baby last Feb. So I lost all of the weight I gained during pregnancy, without a ton of effort I just ate healthier and slowly started to exercise again. the problem is, now I'm trying hard to lose more and I'm stuck at that weight I was right before getting pregnant and it's not coming off! I now go to the gym, I do weights and cardio and eat healthy (also in a caloric defecit, i eat about 1500 cal/day) so how can I get rid of these 20 lbs?